1. Field of the Invention
This invention relates to a process for producing biopolymer nanoparticles and in particular, starch nanoparticles.
2. Description of the Related Art
U.S. Pat. No. 6,677,386 (which corresponds to WO 00/69916) describes a process for producing biopolymer nanoparticles, which in one form are starch nanoparticles. In the process, the biopolymer is plasticized using shear forces, and a crosslinking agent is added during the processing. After the processing, the biopolymer nanoparticles can be dispersed in an aqueous medium. One version of the process results in starch nanoparticles which are characterized by an average particle size of less than 400 nanometers.
U.S. Pat. No. 6,677,386 notes that the nanoparticles can be used as a matrix material wherein the matrix material may be a film-forming material, a thickener, or a rheology modifier, or an adhesive or an adhesive additive (tackifier). The nanoparticles or dispersions thereof may also be used for their barrier properties, as a carrier, as a fat replacer, or as a medicament for mitigating dermal disorders. Further examples of applications for the nanoparticles or dispersions thereof are in the paper-making and packaging industry, or in agriculture and horticulture. The nanoparticles can also be used as excipients or carriers in medicines, where they may be complexed or covalently coupled to active substances such as slow-release drugs. The nanoparticles can also be processed into a foam at relatively high density.
Other uses of the nanoparticles of U.S. Pat. No. 6,677,386 can be found in: (i) U.S. Patent Application Publication No. 2004/0011487 which describes the use of the starches as a wet-end additive in papermaking pulp slurry, or applied to the surface of the paper as a surface sizing agent; (ii) U.S. Pat. No. 6,825,252 which describes the use of the starches in a binder in a pigmented paper coating composition; (iii) U.S. Pat. No. 6,921,430 which describes the use of the starches in environmentally friendly adhesives; and (iv) U.S. Patent Application Publication No. 2004/0241382 which describes the use of the starches in an adhesive for producing corrugated board. The disclosure of these patents and applications, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein.
It can be seen that the nanoparticles prepared by the process of U.S. Pat. No. 6,677,386 have numerous uses. Furthermore, additional uses will likely be found in the future. As a result, the demand for larger quantities of the biopolymer nanoparticles will continue to increase. However, there are concerns that the process described in U.S. Pat. No. 6,677,386 may not be able to keep up with the increasing demand for the biopolymer nanoparticles.
Therefore, there is a need for an improved process for producing larger quantities of biopolymer nanoparticles and in particular, starch nanoparticles.